1. Field of the Invention
The present invention relates to a system and method for a scalable optical cross-connect in an optical telecommunications system and, in particular, an optical cross-connect system and method that efficiently and economically handle capacity upgrades.
2. Description of the Related Art
Advances in computer and network technology have made it simple and convenient to send and receive information throughout the United States, and indeed throughout the world. Internet usage has expanded rapidly within the past few years, and the information available and the number of people able to access that information has grown exponentially. It is now common to collect a variety of information through the Internet, including educational, consumer, recreational, and commercial information. More transactions are being conducted through the Internet and more business, medical, and government transactions are becoming paperless. Currently, huge volumes of information must be transferred to meet Internet and business communication demands.
As computer technology advances and today""s possibilities become tomorrow""s reality, the demand for information is expected to increase. For example, graphics and images require a significantly greater volume of data than does simple text. As quality graphics and real-time image processing applications become commonplace, additional huge volumes of data will need to be transferred rapidly. Moreover, video-on-demand services, video telephone and teleconferencing services, and medical image archiving and retrieval, to name just a few, are expected to expand in the coming years.
The telecommunications network serves as the pipeline through which the bulk of information is transferred. Network service providers have begun to turn to new types of optical equipment ideally suited to meet current and fixture demands for information. One such type of optical equipment is the optical cross-connect switch. Optical cross-connects (OXCs) perform switching operations in networks, such as ring and mesh networks, so that information can travel to its intended recipient. Optical cross-connects enable network service providers to switch high-speed optical signals efficiently. For example, an OXC stationed in Chicago may receive incoming information from New York and strip off the received information destined for Chicago, switch a portion of the received information to Houston, and switch another portion of the information to San Francisco.
However, optical switching equipment is expensive. There remains a need for systems and methods that can handle the information volumes anticipated in the near-term and that are capable of economically expanding to meet long term demands.
The present invention has been made in view of the above circumstances and has as an object to provide a simple and economical system and method for scaling optical communications equipment.
A further object of the invention is to provide a versatile optical cross-connect design capable of economically scaling to meet future needs.
A further object is to provide an efficient and economical method for upgrading the capacity of an optical cross-connect.
Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises an optical cross-connect in an optical telecommunications network comprising a plurality of first stage switch matrices, first and second cabinets, a plurality of middle stage switch matrices having input ports and output ports, and a plurality of last stage switch matrices having input ports and output ports. Each of the first stage switch matrices have a plurality of input ports, each input port receiving an input communication signal, and a larger number of output ports, where the first stage switch matrices switch the input communication signals to selected output ports. Each of the first and second cabinets have a predetermined number of bays, with at least one of the first stage switch matrices housed in a bay of the first cabinet and at least one of the first stage switches housed in a bay of the second cabinet. The input ports of the middle stage switch matrices are coupled to the output ports of the first stage switch matrices for receiving communication signals output from the first stage switch matrices. The middle stage switch matrices switch communications signals received at their input ports to their output ports. The input ports of the last stage switch matrices are coupled to the output ports of the middle stage switch matrices for receiving communication signals output from said middle stage switch matrices. The last stage switch matrices switch communications signals received at their input ports to their output ports. In addition, the middle stage itself can be recursively a multistage switch.
The invention further comprises an optical telecommunications network comprising a plurality of network nodes interconnected via fiber optic links, wherein at least one of the network nodes includes an optical cross-connect. The optical cross-connect includes a plurality of first stage switch matrices, first and second cabinets, a plurality of middle stage switch matrices having input ports and output ports, and a plurality of last stage switch matrices having input ports and output ports. Each of the first stage switch matrices have a plurality of input ports, each input port receiving an input communication signal, and a larger number of output ports, where the first stage switch matrices switch the input communication signals to selected output ports. Each of the first and second cabinets have a predetermined number of bays, with at least one of the first stage switch matrices housed in a bay of the first cabinet and at least one of the first stage switches housed in a bay of the second cabinet. The input ports of the middle stage switch matrices are coupled to the output ports of the first stage switch matrices for receiving communication signals output from the first stage switch matrices. The middle stage switch matrices switch communications signals received at their input ports to their output ports. The input ports of the last stage switch matrices are coupled to the output ports of the middle stage switch matrices for receiving communication signals output from said middle stage switch matrices. The last stage switch matrices switch communications signals received at their input ports to their output ports.
The present invention further includes a method for scaling an optical cross-connect to a larger capacity, where the optical cross-connect includes first stage working switches, middle stage working switches having inputs coupled to outputs of the first stage working switches, and last stage working switches having inputs coupled to outputs of the middle stage working switches. The first, middle, and/or last stage switches can be formed by multistage switches themselves. The method comprising the steps of coupling the outputs of the first stage working switches and outputs of additional first stage working switches to inputs of replacement middle stage working switches, and coupling the inputs of the last stage working switches and inputs of additional last stage working switches to outputs of the replacement second stage working switches.
In addition, the present invention allows the complete replacement of the entire switch with an all-optical fabric that may have a smaller number of ports, but that allows for greater scalability because of its photonic nature. The individual ports can be run at higher bit rates.
The present invention further provides a communications switching apparatus for an optical telecommunications network including a plurality of first stage switch matrix cards, each having at least one first stage switch matrix with a plurality of inputs, each input receiving an input communication signal, and a larger number of outputs, where said first stage switch matrices switch the input communication signals to selected outputs; a plurality of last stage switch matrix cards, each having at least one last stage switch matrix with inputs and outputs, wherein said last stage switch matrices switch communications signals received at their input ports to selected output ports thereof, a frame having a first, second, and third groups of slots, wherein the first stage switch matrix cards are received in the first group of slots and the last stage switch matrix cards are received in the third group of slots, the second group of slots configured to receive middle stage switch matrix cards and optical extender module cards, the middle stage switch matrix cards each having at least one middle stage switch matrix having inputs and outputs, wherein the middle stage switch matrices switch communications signals received at their input ports to selected output ports; and a backplane coupled to the first stage switch matrix cards and the last stage switch matrix cards (1) for coupling the outputs of the first stage switch matrices to the inputs of the middle stage switch matrices and for coupling the outputs of the middle stage switch matrices to the inputs of the last stage switch matrices when the middle stage switch matrix cards are received in the second slots, and (2) for coupling communication signals from the outputs of the first stage switch matrices to the optical extender module cards and for coupling external communication signals received by the optical extender module cards to the inputs of the last stage switch when the optical extended module cards are received in the second slots.
The present invention further includes an optical communications switching apparatus for an optical communications network, comprising opto-electronic receivers for receiving optical signals on a plurality of optical fibers; an electronic switch matrix for switching electronic signals received from the first opto-electronic receivers, the electronic signals derived from the optical signals; and an optical switch matrix for switching signals from the electronic switch and optical signals from at least one optical fiber.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.